共查询到18条相似文献,搜索用时 828 毫秒
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报告了在 P_x∶P_y=0,0.5和1三种双轴载荷作用下,对倾斜角等于0°、30°和45°的表面裂纹所作的疲劳扩展研究。讨论了表面裂纹扩展速率的计算方法,指出必须考虑不同的裂纹倾斜角和不同的双轴载荷比造成的裂纹扩展驱动力的变化对斜表面裂纹扩展速率的影响。因而采用裂纹投影法来处理斜表面裂纹的疲劳扩展问题并提出了修正的 Paris 方程。按照修正的 Paris 方程,根据不同的双轴载荷比和裂纹倾斜角分组整理了试验数据,并作了回归分析、假设检验,给出了含表面裂纹的16MnR 板材在三种不同的双轴载荷比情况下的裂纹扩展速率方程。 相似文献
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研究了双轴向应力状态下Ⅰ型穿透裂纹的疲劳扩展规律,采用构形合理且经精确标定应力强度因子值的双向十字形试样,在电液伺服双轴向疲劳试验机上对低合金钢(16MnR)进行了多种载荷比的疲劳裂纹扩展速率试验,得到了双轴向应力状态下的Paris方程,为目前按缺陷评定规范依据单轴向疲劳试验所得数据对工程构件进行疲劳评定提供参考数据,并就当前研究者们对于双向应力场中横向载荷对疲劳裂纹扩展行为的影响的不同看法进行分析探讨。 相似文献
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电工陶瓷材料裂纹扩展规律的研究 总被引:2,自引:0,他引:2
本文应用双扭法研究了四种电瓷材料静态疲劳裂纹扩展规律。试验结果表明:在空气介质中,所有试验电瓷材料均存在明显的裂纹亚临界扩展现象,且随裂纹尖端应力强度因子(K_1)增大呈现三个阶段关系。在不同介质中,裂纹扩展的敏感性按下列顺序变小:水、空气和煤油。试验还表明电瓷材料静态疲劳裂纹扩展规律与材料的配方、环境和受力等因素有关。 相似文献
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研究了双向载荷作用下对焊接头表面裂纹的疲劳扩展规律。采用经精确标定应力强度因子幅值的双向十字形试样,在电液伺服双轴向疲劳试验机上对母材分别为16MnR 和 Q235-B 这两种钢的对焊试板进行了疲劳裂纹扩展试验。同时,将其结果分别与单向应力下对焊接头及母材的疲劳扩展速率进行了比较,为制定我国在役压力容器缺陷评定规范提供了参考数据。 相似文献
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首先进行了16Mn板材半椭圆表面裂纹疲劳扩展试验。试验结果表明,采用Newman-raju应力强度因子时,表面裂纹深度方向和表面方向的扩展速率均符合Paris公式。在此基础上,从Newman-Raju应力强度因子计算式和Paris疲劳裂纹扩展速率公式出发,通过理论和数值分析,建立了3类表面裂纹在受拉伸、弯曲、和拉弯组合加载下的疲劳扩展形貌统一表达式,并通过疲劳试验结果对其进行了考核。结果表明,采用统一表达式预测裂纹形貌的各项统计指标均优于其他两种表达式 相似文献
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玻璃在平面双向和单向应力状态下慢裂纹扩展特性 总被引:1,自引:0,他引:1
采用热弹性力学方法对含裂纹的玻璃薄片在双向和单向平面拉和下的亚临界裂纹扩展进行了观测和研究。该实验方法使得玻璃、陶瓷等危性材料的双向拉伸,直通裂纹预制和裂纹扩展过程记录这3个难度大的实验得以完成。对60多个玻璃试件的断裂阻力随载荷速度的变化进行了观测和分析,从而较精确地了解了玻璃在平面和状态下的阻力曲线和断裂特性。 相似文献
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Guolong Meng Jiaqi Hu Zhenduo Liu Hong Gao Lilan Gao 《Polymer Engineering and Science》2021,61(6):1791-1801
Polyether ether ketone (PEEK) has become a promising material in total joint replacement. However, it still faces the risk of fatigue fracture during service. In this paper, the effects of biaxial stress ratio λ, cyclic stress ratio R, and load phase difference θ on fatigue crack propagation (FCG) behavior of PEEK are investigated. In the case of vertical cracks, results show that the FCG rate of PEEK increases with the R value, while decreases with the increase of λ value. Furthermore, the effective stress intensity factor range ΔKeff can uniformly describe the biaxial FCG behavior at different cyclic stress ratios. In the case of 45° slant cracks, compared with mode-I intensity factor range ΔKI, the energy release rate range ΔG is more accurate for describing the FCG behavior under various load phase differences. In addition, the investigation on the 45° crack propagation path shows that a bifurcated Y-shaped crack appears under 180° load phase difference, while no bifurcated crack appears under 90° load phase difference and uniaxial loading. Three different methods are used to predict the crack propagation path. The comparison results show that the maximum circumferential stress (MTS) criterion can well predict the crack propagation path under out-of-phase biaxial loading and uniaxial loading. 相似文献
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Kiyohiko Ikeda Hisashi Igaki Yoshinobu Tanigawa Koichiro Tagashira 《Journal of the American Ceramic Society》1990,73(7):2114-2116
Equibiaxial stress effects were observed in constant stressing rate tests of indented soda-lime glass in a water environment. To discuss whether the equibiaxial stress effects on fracture strenght in a water environment were caused by the blunting of crack tips by chemical reaction between the glass and moisture, the specimens with controlled surface flaws soaked in hot water to make the crack tip blunt were fractured under both uniaxial and equibiaxial tensile stresses under both vacuum and air environments. The biaxial strengthening observed under restricted subcritical crack growth indicates that equibiaxial stress effects in a water environment are caused by the rounding of the initial crack tip. 相似文献
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Prediction of ring crack initiation in ceramics and glasses using a stress–energy fracture criterion
Roman Papšík Oldřich Ševeček Éric Martin Raúl Bermejo 《Journal of the American Ceramic Society》2023,106(7):4329-4342
Crack initiation in brittle materials upon spherical indentation is associated with the tensile radial stresses during loading. However, location of crack onset often differs (offset) from the site of maximal stress. In addition, experiments reveal a strong dependency of crack initiation forces on geometrical parameters as well as the surface condition of the sample. In this work, a coupled stress–energy fracture criterion is introduced to describe the initiation of ring cracks in brittle materials, which takes into account the geometry of the contact and the inherent strength and fracture toughness of the material. Several experiments reported in literature are evaluated and compared. The criterion can explain the location offset of the ring crack upon loading, as observed in various ceramics and glasses. It also predicts the ring crack initiation force upon contact loading, provided that surface compressive stresses, introduced during grinding or polishing processes, are taken into account. Furthermore, the stress–energy criterion may be employed to estimate the surface residual stress of ceramic parts, based on simple contact damage experiments. 相似文献
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Daniel P. DeLellis Nicholas A. Mecholsky John J. Mecholsky Jr George D. Quinn 《Journal of the American Ceramic Society》2020,103(9):5283-5290
Many fractography techniques involve precise measurements of features on the fracture surface and can be difficult to perform in the field, or rapidly. Macroscopic crack branching observations offer a more robust and forgiving method of analysis, but often are not strongly correlated with standard fractography techniques. In this study, the crack branching patterns of annealed borosilicate glass disks previously fractured in biaxial tension were analyzed using fractal methods and compared with more typical fracture surface measurement techniques. The results confirm that the fractal dimension of macroscopic crack branching (called the Crack Branching Coefficient) increases with increasing failure stress, as has been shown with other brittle materials. In addition, the existence of a threshold stress previously reported was confirmed using new techniques. The findings herein can be used to further increase the fidelity of fractography-based failure analysis of brittle materials. 相似文献